The present invention relates to a cutter bit assembly of the type utilized for excavating machines. As employed herein the term "excavating machine" includes mining machines, road scarifying machines, concrete cutting machines and the like. The present invention is concerned with a retainer system incorporating a hollow, cap-like retainer made from a polymeric material with adapted to be detachably connected to the terminal free-end of the cutter bit shank so as to prevent axial dislodgment of the shank and hence, the cutter bit upon excavating use thereof. A typical prior art retainer, for example, disclosed in U.S. Pat. No. 3,820,848 wherein a conventional type C-ring or hog ring is utilized to retain the cutter bit in the mounting block. As known in the art, this retainer ring construction is intended to limit movement of the cutter bit in an axial direction relative to the mounting block.
The present invention has particular application with cutter bit assemblies wherein the cutter bit has a generally conically shaped nose portion and an elongated, reduced diameter cylindrical shank portion, and with the shank portion being adapted to be disposed for rotatable movement within the corresponding axial bore in the mounting block. When the excavating machine is in operation, it has been official that the bits rotate in the bore or socket provided in the mounting block. This allows a wear upon the bit and the carbon insert (carbide) to be distributed generally evenly allowing the bit to retain its symmetry thereby providing substantially continuous sharpness of the bit and carbide insert during operation thereof. Recently, there has been provided a generally, resilient wear sleeve retainer element that is disposed between the shank of the bit and the bore or socket of the mounting block wherein the bit is allowed to rotate within the wear sleeve which is frictionally held on the inside wall of the bore or socket while retaining the cutter bit in its properly oriented working position on a excavating wheel, for example. Such an assembly is disclosed in U.S. Pat. No. 4,201,421.
Herefore, difficulties have been encountered in an effort to rotatably mount the cutter bit with prior retainer systems. Systems snap-type retainers are not completely effective for minimizing the wear on the back of the mounting block to the point where the tools develope a substantial amount of freedom of movement in the axial direction in the mounting block. Also, such prior snap-ring retainers generally require a special snap-ring tool for assembly and disassembly and are relatively costly to produce.
This application is related to Applicants co-pending application Ser. No. 610,618 filed May 16, 1984 wherein various retainer systems are disclosed in conjunction with a new and improved conical bit having a generally mushroom-shaped nose portion.